1. Field of the Invention
The present invention relates to an obstacle detection device that is mountable on a surface of a movable body.
2. Description of the Related Art
A conventional obstacle detection device includes at least one transmitting element and a plurality of receiving elements arranged in an array. The transmitting element outputs a transmitting wave. A reflected wave that is the transiting wave reflected by an obstacle is received with the receiving elements. Accordingly, the obstacle detection device detects a distance to the obstacle and a direction of the obstacle. In a case where an obstacle detection device is mounted on a vehicle, for example, the obstacle detection device can detect an object in the rear of the vehicle as an obstacle when the vehicle moves rearward. A wall and a pole may become an obstacle when the vehicle moves rearward. When a wall is located in the rear of the vehicle, the vehicle may collide against the wall at a large area in a width direction of the vehicle. When a pole is located in the rear of the vehicle, the vehicle may collide against the pole at a small area in the width direction of the vehicle. In a case where an obstacle detection device is mounted on a vehicle, the obstacle is generally disposed on a surface of a vehicle body. For example, the obstacle detection device is disposed on a surface of a rear bumper of the vehicle.
In a case where an obstacle is a wall that provides a planar surface in a direction detecting direction, a reference point of the obstacle that is used when the obstacle detection device calculates a distance to the obstacle is a point where a perpendicular line from the obstacle detection device crosses the planar surface. When the vehicle moves rearward in a direction perpendicular to the planar surface of the wall, a bumper surface of the rear bumper is substantially parallel to the surface of the wall. Thus, a distance between a portion of the bumper surface of the rear bumper and the surface of the wall is the shortest distance, and the calculated distance to the object is substantially same as the shortest distance between the vehicle and the wall. When the vehicle moves rearward in an oblique direction to the surface of the wall, the bumper surface of the rear bumper is not parallel to the surface of the wall. Thus, a distance between an end of the bumper surface of the rear bumper and the surface of the wall is the shortest distance, and the calculated distance to the obstacle is not same as the shortest distance between the vehicle and the wall.
In order to solve the above-described issue, it is required to determine a shape of the obstacle and a relative position of the obstacle to the vehicle as well as the distance to the obstacle and the direction of the obstacle and to calculate the shortest distance based on the shape of the obstacle and the relative position of the obstacle to the vehicle. For example, JP-A-2006-343309 discloses an obstacle detection device in which a history of a vehicle position at a time when the obstacle detection device detects an obstacle is stored, a correlation between the history of the vehicle position and running information including a vehicle speed and a steering angle is updated, and thereby a shape of the obstacle is determined.
In the above-described obstacle detection device needs to receive the running information including the vehicle speed and the steering angle from an external device. Thus, the obstacle detection device needs a configuration for receiving the information from the external device and a configuration for processing the information from the external device.